1. Field of the Invention
The present disclosure relates to a high breakdown-voltage element mounting board formed mainly of a metal, a semiconductor module using the element mounting board, and a method for fabricating the element mounting board and the semiconductor module.
2. Description of the Related Art
In recent years, the reduction of environmental load is often discussed in the press, and many corporations are doing their researches on the reduction of energy in particular and on highly efficiency semiconductor modules from various angles.
Among those semiconductor modules and semiconductor elements, a semiconductor element for use in a high power application is particularly used to drive the motor of a refrigerator, a washing machine, an air conditioner or the like used at home. The power consumed by these home electric appliances is a factor not to be missed if the power consumed thereby is summed on a global scale. Accordingly, the recent development to achieve the energy saving in various aspects involves, for example, the reduction of standby power, the use of LED lighting, the inverter control in each home electronic appliance.
An important factor not to be missed in the reduction of power is the heat radiation. In other words, semiconductor elements generate heat when they are driven. If such heat is not sufficiently radiated from the semiconductor elements, the semiconductor elements will suffer a high temperature and cannot enhance the drive current, resulting in a large power loss. In order to improve the heat radiation, every effort is made to raise the heat release property by using a copper (Cu) frame, a metallic substrate and additionally a large heat radiation fin, for instance.
In the conventional practice, a semiconductor module including a metallic substrate in an element mounting board is constructed as follows. That is, an anodic oxide film is formed on the surface of an aluminum substrate, for instance, and a wiring and a semiconductor element are mounted on this anodic oxide film with an insulating resin layer disposed between the anodic oxide film and the semiconductor element. In the conventional method for fabricating a semiconductor module, the anodic oxide film is formed on the surface of a large-sized substrate through anodic oxidation, and a wiring pattern is formed on the anodic oxide film via the insulating resin layer. After this, the semiconductor element is mounted thereon and then the large-sized substrate (substrate sheet) is separated into individual pieces.